Syria: Who are Hayat Tahrir al-Sham, the rebels seizing control of Aleppo?

The war in Syria has for the past four years felt as if it were effectively over.

President Bashar al-Assad’s rule is essentially uncontested in the country’s major cities, while some other parts of Syria remain out of his direct control.

These include Kurdish majority areas in the east, which have been more or less separate from Syrian state control since the early years of the conflict.

There has been some continued, though relatively muted unrest, in the south where the revolution against Assad’s rule began in 2011.

In the vast Syrian desert, holdouts from the group calling themselves Islamic State still pose a security threat, particularly during the truffle hunting season when people head to the area to find the highly profitable delicacy.

And in the north-west, the province of Idlib has been held by jihadist and rebel groups driven there at the height of the war.

The dominant force in Idlib is the one that has launched the surprise attack on Aleppo, HTS.